How can I do a 10 khz square wave with LtSpice ?

[tessier]

Hi

How can I generate a 10 khz square wave with LtSpice ? (50 % duty cycle)

And how for a 31 khz square wave ?

Thanx

Paul

 

[sawreyrw]

Use a pulsed voltage source with the correct times. Note that Trise and Tfall should not be 0.

 

[tessier]

Hi

I don't know how to set the LtSpice pulsed voltage source for those frequency square waves.

Thanx

Paul

 

[ingenieus]

Add a voltage source to your circuit. Right click on it. A window like below should pop up. The values below gives a 10kHz square wave. Adjust for 31kHz.

 

[tessier]

Hi

Is it the Tperiod or the Ncycles that I have to adjust to get 31 khz ?

Thanx

Paul

 

[Tekko]

You can leave Ncycles alone since thats only how many cycles it'll give before it stops, leaving it blank will make a continous pulse train.

On Nperiod you put in the equivalent time for 31 kHz and Ton will be half of that value to define 50% duty cycle.

Rise and fall can be set to 1µ.

 

[jaycee]

Tperiod would be 1/31000.
Ton will be half that

You may do:
Ton = {0.5/<value in Hz>}
and
Tperiod = {1/<value in Hz>}

I would also use rise/fall times of 0.01u as this will give you a "perfect" square wave with no percievable rise/fall time.

 

[tessier]

Hi

So, to get 31 khz, I set Tperiod to 31u and Ton 15u ?

Thanx

Paul

 

[jcx]

for symmetry you need to set Ton = (1/2)*(1/f) - t_rise

use curly brackets, .param to save typing

 

[Pano]

Moved to Software forum

 

[tessier]

for symmetry you need to set Ton = (1/2)*(1/f) - t_rise

use curly brackets, .param to save typing

Hi

I've try your param but it was not work ok.

Can you show me a capture image of the LtSpice Fonctions window showing the pulse parameters.

Thanx

Paul

 

[jcx]

clik on the attachment thumbnail?

the line:

.param f = 31k, t_edge=1u

has to be entered in the <.op> tool pop up window (far right on toolbar)

the line:

PULSE(-1 1 0 {t_edge} {t_edge} {1/2/f-t_edge} {1/f})

is the "value" entry for the Vsource, usually entered in the dialog window but can be pasted in the pop up box when rt clking on the value

[edit: paste the line in a Vsouce "Value", then rt cik Vsource body, you will see filled in parameters in window]

add new named params to control additional sources, you can have f1 = 10k, f2 = 31k on the same schematic with the Vsources each using the appropriate parameter name

 

[tessier]

Hi

I was meaning the LtSpice Fonctions window like the image I show here.

Thanx

Paul

 

[sawreyrw]

tessier,

Can't you figure out the period of a 31 KHz square wave? If not, you have a lot of work to do before you will learn anything from LTspice.

Rick

 

[jcx]

honest questions without pretense are/should be welcomed

 

[tessier]

Hi

The 31 khz square wave are working but it's all down on the negative side like you can see in my image.

I've only used Ltspice with sine wave in amps simulations.

Thanx

Paul

 

[sawreyrw]

OK Paul, here's some useful information. The period of a 31 KHz square (or sine) wave is 1/31 KHz=3.226 us. So to make a 31 KHz square wave in LTspice set Tperiod=3.226us, trise=.01u, tfall=.01us, and Ton=1.6us.

 

[sawreyrw]

jcx,

You answer is way to complex for newbies, and not very useful.

Rick

 

[gaetan8888]

OK Paul, here's some useful information. The period of a 31 KHz square (or sine) wave is 1/31 KHz=3.226 us. So to make a 31 KHz square wave in LTspice set Tperiod=3.226us, trise=.01u, tfall=.01us, and Ton=1.6us.

Hello sawreyrw

There is a small typo error.

1/31 KHz should give 32.26 us

Bye

Gaetan

 

[jcx]

yes it shows some more advanced spice feautures, but I thought I was clear on how they can be copy/pasted from my post

learning how to get the Spice SW do the calculation seems worth the complication if you're using oddball frequencies with primes too big to count on fingers in their factorizations